Definition of drought, Causes of drought, measures for water conservation and
augmentation, drought contingency planning. Water harvesting: rainwater
collection, small dams, runoff enhancement, runoff collection, ponds, tanks.
1. MODULE- V
Drought Management and
Water Harvesting
Prepared by
Bibhabasu Mohanty
Dept. of Civil Engineering
SALITER, Ahmedabad
2. Contents
Definition of drought, Causes of drought,
measures for water conservation and
augmentation, drought contingency
planning.
Water harvesting: rainwater collection,
small dams, runoff enhancement, runoff
collection, ponds, tanks.
3. Introduction
Normal, recurrent feature of climate
Occurs everywhere, vary from region to region.
Originates from deficiency of precipitation.
Impact on ecosystem and agricultural of affected
region.
Drought leads to food insecurity, famine,
malnutrition, epidemics and displacement of
populations.
5. Causes of drought
Reduced rainfall results in drought.
Occurs because water vapour not brought by air
currents to right areas at right times.
Unusual currents of cold and warm water in
oceans creates high pressure. El Nino causes
drought in Asia.
Mountain prevent wind from blowing moisture
to needy region.
6. In India when water vapour moves from east to
west, water vapour does not leave Indian ocean
causes drought.
Human activity directly trigger over farming,
excessive irrigation, deforestation.
Global warming result in rainfall in some areas
and drought in some areas.
7. Drought contingency planning
To provide contingency plans to manage
drought and emergency conditions.
To continue to deliver a cost effective, adequate,
safe and reliable supply of water.
The provision of credit or cash/food for work
Maintaining water supply for animals and
humans
8. Maintaining cereal availability
Human and livestock health service provision
Support for private sector
Provide fodder for affected stock
Flexible taxation systems for affected people
10. Drought contingency planning for
implementation:
Overall drought policy, setting out plans
objectives of minimizing the impact of drought
Set plans for specific mitigation, relief and
rehabilitation measures
Construction of dams and additional reservoirs
for supply of water.
Cloud seeding- artificial rain
11. Desalination of sea water for irrigation or
consumption.
Drought monitoring by total rainfall levels and
total usage levels
Land use by carefully planned crop rotation
Outdoor water use restriction
Rainwater harvesting
Recycled water
Relief works
Disease prevention and control
12. • Contingency planning done by Govt.
Policy issues, national, regional and district level
rural development infrastructure
input supply, marketing and farm advisory
services
• Non- Govt.
NGO’S
Rural institutions
Private sectors
13. Augmentation of water
It includes methods for providing an entirely
new supply of fresh water and techniques for
increasing utility of available supplies of water.
New supply of water include weather
modification.
Weather modification done to increase
precipitation and decrease Evapotranspiration.
Cloud seeding done to increase precipitation.
15. Available water supplies increased by conservation
of available water supplies.
Agricultural water requirements can be reduced
by reducing conveyance losses, and discouraging
wasteful irrigation techniques.
Technique should be developed to reduce water
consumption in home and industry.
Evaporation losses from small reservoirs can be
reduced by providing roofs.
16. Reclamation and reuse of waste water can be
encouraged.
Evaporation loss in ground water is less. Use of
ground water storage reservoir in conjunction
with surface storage reservoirs.
Infiltration losses can be reduced by sealing the
soil surface useful in arid regions.
Water harvesting done by collecting from roof
top, pavements, constructing small storage.
17. Measures for water conservation
Goals of water conservation efforts include:
Sustainability- ensure availability for future
generations
Energy conservation- world 15% energy
production dependent on water management.
Habitat conservation- preserve fresh water
habitat, migrating waterfowl.
18. Benefits of water conservation:
Save water save money.
Reduction in excess water use reduce waste
water generation, reduce overflowing of gutter.
Ecosystem and habitat protection.
Helps in improving quality of drinking water.
20. Domestic conservation
Repair all leaks quickly
Turn off water when not in use
Use conserving appliance which use low volume
water for domestic use
Local bodies should install water meter and
encourage water pricing.
21. Industrial conservation
Use cooling system which use less water.
Reuse of cooling water for irrigation or other
purposes.
Install in plant treatment measures for treating
the waste water or effluent.
22. Agricultural (irrigation) conservation
Improved irrigation methods such as sprinklers
or drip irrigation.
Water required for agricultural considerably
reduced by reducing conveyance loss.
Evaporation losses from small reservoirs can be
reduced by providing roofs over them.
Use of lined canals which reduce seepage and
evaporation.
23. Use of ground water storage reservoir in
conjunction with modern surface storage
reservoirs to reduce evaporation loss, in arid
regions.
Price agricultural water to encourage
conservation.
Infiltration losses reduced by sealing soil surface.
Water harvesting in arid regions.
24. For conservation of water the following
structures can be constructed:
Earthen bund
Gully plugging
Check dam
Khet talawadi
29. Water harvesting
Collection of rain water called water harvesting.
Rainwater harvesting is accumulation and
storing of rainwater for reuse, before it reaches
aquifer.
Water collected from roofs of houses, schools,
local institutions make important contribution.
Water collected from ground, called storm water
harvesting.
30. Benefits of rainwater harvesting
Increase water availability
Checks declining water table
Environmental friendly
Improves water quality of ground water
Surface water runoff conservation
Prevents soil erosion and flooding in urban area
31. Rainwater harvesting technique
Rainwater collection – Roof top rainwater
harvesting
Runoff collection – Surface runoff harvesting
Recharge to ground water
Runoff enhancement
32. Roof top rain water harvesting
Rainwater captured from roof catchments and
stored in sub surface ground water reservoir.
Objective is to make water available for future
use.
Useful in dry land, hilly, urban and costal areas.
33. Components of roof top rainwater harvesting
a collection area
a conveyance system
storage facility
a delivery system
Storage reservoir expensive part, careful design
and construction required.
First rainwater should be flushed or diverted.
36. Surface runoff harvesting
Surface runoff harvesting is traditional
technique.
Small dams, ponds, tanks are used.
Used for irrigation, domestic, livestock use.
37. Small dams
Small dams/check dams constructed in natural
channel to impound the runoff water up to
certain depth.
Impounded water slowly infiltrate into soil and
recharge ground water.
38. Ponds and reservoirs
Impounding type and dug-cut type ponds
constructed.
In impounding type, a retaining wall or dam is
constructed to block the flow of water in a
natural storm.
In dug-cut type area is excavated to store the
runoff.
Reservoirs requires water storage area, spillways
and earth embankment.
39. Storage tank
Surface or above ground tank
Subsurface or underground tank
Storage tanks require
Solid secure cover
Coarse inlet filter
Overflow pipe
Manhole, sump and drain to facilitate cleaning
Outlet system, tap or pump
40. Recharge to ground water
The structures generally used:
Pits
Trenches
Dug well
Hand pumps
Recharge well
Spreading techniques
Underground reservoirs
41. Runoff enhancement
Can be done by increase precipitation.
Seeding generally done to increase precipitation.
Precipitation can be increased by 10% by cloud
seeding.
Lumb demonstrated that increase in annual
runoff (∆R) due to small increase in precipitation
(∆P) is given by
∆R= ∆P (0.29+1.2 R/P)
R= mean runoff, P= mean precipitation
42. Methods for runoff enhancement:
Cloud seeding
Enhancement by paved surfaces.
Surface of drainage basin effect on runoff. Bare
surface give more runoff.
Drainage basin located on windward side of
mountain produce more runoff.
Runoff affected by geology of drainage basin.
Pervious soil yield less runoff.
43. Drainage basin has larger no of natural
depressions, which deposited by other material
then runoff at basin increases.
More Human activity, more load on soil, reduce
infiltration, hence increase runoff.
45. 1. Discuss various causes of drought
2. Discuss drought contingency planning and its
importance.
3. Explain augmentation of water and its various
methods.
4. Explain water conservation and its various
methods.
5. Discuss importance of rainwater harvesting and
explain various techniques used for it.